For decades, Mille Lacs Lake was managed in much the same way as other large Minnesota lakes. The fish population was monitored by test-netting and fishing success with an annual creel survey. Together, these surveys provided the DNR the information it needed to detect changes in fish populations and make appropriate management decisions.
With the advent of treaty management, however, a court-approved allocation system now requires the DNR to assess the walleye population with much more precision. Instead of tracking the “relative” abundance of walleyes through statistics such as number and weight of walleyes per gill net and catch per man-hour of fishing, they are now required to measure the “absolute” abundance by making an annual population estimate. This estimate is then used to establish a “safe harvest level” that will prevent overexploitation of the walleye population.
Once the DNR agreed to a treaty-management system requiring annual population estimates, they were faced with the immense problem of how to make meaningful estimates using the data they had available. So they devised a complex computer model, called the VPA (Virtual Population Analysis) that would generate the number they needed to satisfy their responsibility to the Court.
But even the biologists who devised the VPA have little confidence in its ability to generate an accurate population estimate. The problem is, every piece of information fed into the VPA has a wide margin of error, most of which cannot be accurately measured. So the combined error is unknown, and so is the usefulness of the VPA. The DNR continues to “tune” its model in an attempt to improve its accuracy, but the underlying problem of insufficient or unreliable data cannot be solved anytime soon.
The purpose of this paper is to closely examine the present treaty management system, identify its weaknesses and suggest a common-sense management solution that will not only maintain a healthy walleye population, but also satisfy the Court and protect the interests of sport anglers and Band members.